Vallisneria is a genus of aquatic plant, commonly called eelgrass or tape grass. The genus has 6-10 species that are widely distributed, but do not grow in cold regions.
From my own experience growing this plant i can tell you its very easy to grow, fine in lower light level tanks, and does grow best with some root tabs. Provide good water flow around their tall thin foliage, and you should have runners in no time. Especially great for a backdrop.
I have some in a coldwater tank with medium light and a laterite and sand substrate. I can almost watch it growing each day! I have found it very very easy to grow and it has sent out quite a few runners. A lovely plant... I recommend you try it.